DE102012223849B3 - Lighting apparatus e.g. lamp has reflective layer that is located between rear side of diffusion plate and other reflective layer and is provided with glass particles - Google Patents

Abstract

The lighting apparatus (1) has a light transmissive diffusion plate (2) provided with a front side (5), a rear side and an edge surface (3). A first reflective layer is arranged at the rear side of the diffusion plate and is provided with diffusely reflecting color pigments. An LED (4) is optically coupled with the edge surface of the diffusion plate. A second reflective layer is located between the rear side of the diffusion plate and the first reflective layer, and is provided with glass particles. An independent claim is included for a method for manufacturing lighting apparatus.

Description

The invention relates to a lighting device, comprising a light-transmitting scatter plate or diffuser having a front side, a back side and an edge side, on which rear side at least one reflective layer is arranged, and further comprising at least one semiconductor light source, which is optically coupled to the edge side of the diffusion plate. The invention also relates to a method for producing such a lighting device. The invention is particularly applicable to LED modules.

It is a lighting device of the aforementioned type known in which a scattering plate of simple Plexiglas is illuminated by its edge side with light emitting diodes (LEDs) ("edge lighting"). The light radiated in through the edge side is emitted at least partially through the front side and the rear side of the diffusion plate. The back is covered with a white layer as a reflective layer, the white layer having white color pigments. The reflective layer throws the light back into the scatter plate and homogenizes it. From the lighting device as such emitted useful light exits only from the front of the lighting device. For a further homogenization of the brightness distribution of the scattering plate, a diffuser, for. As a milky-white disc, be connected downstream. However, the lighting device has the disadvantage that it has a comparatively low homogeneity of the brightness distribution of the light emitted over the area of the front side. In addition, a light output is rather low.

Furthermore, shows the European patent application EP 0 823 587 A1 an optical fiber lighting device or a light guide display device with a scattering plate, a reflective layer and LEDs, is coupled via the light side into the scattering plate.

It is the object of the present invention to at least partially overcome the disadvantages of the prior art.

This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims.

The object is achieved by a lighting device, comprising a light-permeable scatter plate having a front side, a back side and an edge side, on which rear side at least a first reflective layer is arranged, which has diffusely reflecting color pigments and further comprising at least one semiconductor light source, which optically with the edge side the diffusion plate is coupled, wherein between the back of the scattering plate and the first layer, a second layer is arranged, which comprises particles of translucent material.

This lighting device has the advantage that an additional, strong scattering or reflection of the light emerging at the back is generated by the particles of light-transmitting material of the second layer, resulting in improved homogeneity of the brightness distribution over the surface of the scattering plate, and thus also their Front, effected. In this case, light losses due to the presence of the second layer are negligible. The second layer is thus in particular at least partially translucent.

The lighting device may be a light module, a lamp or a lamp.

In principle, a scattering plate can be understood to mean any body which is able to radiate light coupled into the edge side of the scattering plate to a significant extent over the rear side and the front side. The scattering plate may in particular have a thickness which is considerably smaller, in particular by an order of magnitude, than its extent in its main plane. In particular, the thickness may be constant. The front side and the back side represent the surfaces associated with the main plane. The scattering plate or its main plane may be flat, but is not limited thereto and, for example, may also be curved, eg. B. spherical cap shaped. In addition, a shape of the scattering plate in plan view is not limited and may be, for example, round, oval, square or freeform.

It is a development that the scattering plate has a circular disk-like basic shape.

It is still a development that the scattering plate consists of a transparent plastic, in particular of polymethyl methacrylate (abbreviated PMMA, colloquially referred to as acrylic glass or Plexiglas). The material of the diffusion plate may be, for example, PLEXIGLAS ^® Endlighten Evonik. This is especially suitable for edge lighting and has in the PMMA embedded light diffuser particles, whereby this material is translucent in the non-illuminated state.

It is a particularly preferred development that the material of the diffusion plate PLEXIGLAS ^® Endlighten T or PLEXIGLAS ^® LED Evonik is. PLEXIGLAS ^® Endlighten T has the advantages over PLEXIGLAS ^® Endlighten that it is transparent (has no turbidity) and is decoupled more evenly over the surface. moreover the light is radiated much more sharply at right angles to the front or back, which increases the brightness by 250% when viewed frontally.

Preferably, the at least one semiconductor light source comprises at least one light-emitting diode. If several LEDs are present, they can be lit in the same color or in different colors. A color can be monochrome (eg red, green, blue, etc.) or multichrome (eg, white). The light emitted by the at least one light-emitting diode can also be an infrared light (IR LED) or an ultraviolet light (UV LED). Several light emitting diodes can produce a mixed light, z. B. a white mixed light. The at least one light-emitting diode may contain at least one wavelength-converting phosphor (conversion LED). The phosphor may alternatively or additionally be arranged remotely from the light-emitting diode ("remote phosphor"). The at least one light-emitting diode can be in the form of at least one individually housed light-emitting diode or in the form of at least one LED chip. Several LED chips can be mounted on a common substrate ("submount"). The at least one light emitting diode may be equipped with at least one own and / or common optics for beam guidance, z. At least one Fresnel lens, collimator, and so on. Instead of or in addition to inorganic light emitting diodes, z. Based on InGaN or AlInGaP, organic LEDs (OLEDs, eg polymer OLEDs) can generally also be used. Alternatively, the at least one semiconductor light source z. B. have at least one diode laser.

The fact that the at least one semiconductor light source is optically coupled to the edge side of the scatter plate may mean, in particular, that the scatter plate is edge-illuminated by the at least one semiconductor light source, that is, the light emitted by the at least one semiconductor light source is coupled through the edge side of the scatter plate in this. This can be directly or via at least one intermediate optical element, for. As a lens and / or a light guide happen.

It is an embodiment that the at least one first layer has white color pigments. This allows a color-neutral diffuse reflection. It is a development of which the at least one first layer has absolute white color pigments. The at least one first layer thereby provides an absolute white layer (according to the RAL color gamut). This enables a particularly color-neutral diffuse reflection.

It is still an embodiment that the at least one first layer has multiple layers. When applying several layers, light losses can be reduced, in particular if a layer is not completely opaque. The at least one first layer may, for example, comprise a plurality of (partial) layers of identical material. The multiple layers may have the same layer thickness. For example, the at least one first layer may consist of four superimposed identical layers.

It is still an embodiment that the second layer comprises particles of transparent material. This reduces even lower light loss even further.

The particles may for example consist of ceramic or plastic. It is a particularly preferred embodiment that the particles are glass particles, since these are inexpensive and commercially available in many variations.

It is yet another embodiment that the particles have a maximum extension between 0.2 mm and 0.5 mm. This expansion causes a particularly high scattering effect with low scattering losses. If the particles are spherical, a maximum extent can be understood to mean, in particular, their diameter.

It is also an embodiment that the particles have a rectangular or cuboid shape. This allows a particularly simple and inexpensive production. Under a maximum extent may be understood in particular a largest edge length.

It is a development of that the particles have a cuboid shape with a length of 0.25 mm and a height of 0.1 mm. It is a further development that the particles have a cuboid shape with a length of 0.45 mm and a height of 0.2 mm. The smaller particles cause a more uniform distribution of light or better homogeneity of the emitted light in a near field with a distance of up to 0.5 m from the lighting device, the larger particles a more uniform light distribution in a far field with a distance of more than one meter from the lighting device , Particles of different sizes can also be mixed.

Basically, however, the shape of the particles is not limited and may, for. B. cubic or free-shaped.

It is also an embodiment that the particles of the second layer are embedded in a transparent, in particular transparent, matrix material. a translucent matrix material increases a scattering effect, a transparent matrix material reduces light losses.

It is a development that the transparent matrix material is clearcoat. Clearcoat has the advantages that it is inexpensive, is resistant, has good adhesion, is easy to flow and is easy to apply, in particular to the back of the scattering plate.

It is a development of the fact that the particles have a higher density than the, in particular transparent, matrix material. As a result, the particles can settle after application of the still liquid clearcoat and be arranged closer to the ground. In particular, if the offset with the particles clearcoat is applied to the back of the scattering plate as a substrate, the particles can settle directly on the scattering plate and so a (partial) layer or layer region of scattering particles of higher density in direct contact or in the immediate vicinity of form the scatter plate. It is thus an embodiment that the particles of the second layer are arranged with increased density at the back of the scattering plate.

It is an associated method comprising the step of applying the second layer of transparent material particles embedded in the transparent matrix material to the back surface of the diffusion plate and allowing the particles to settle on the back surface of the diffusion plate. In particular, the particles have a higher density than the matrix material.

It is a development that a ratio of clear coat to particles 95 to 5, in particular of 95 milliliters of clearcoat to 5 grams of glass particles.

Alternatively, the particles of transparent material may be attached directly (without matrix material) to the diffusion plate, e.g. B. by attachment by means of increased pressure and / or temperature, for. B. by a "baking".

As an alternative to particles of transparent material, for. B. also be used in a matrix material air bubbles.

It is yet another refinement that the at least one semiconductor light source has a plurality of semiconductor light sources distributed in particular around the edge of the diffusion plate, in particular equally distributed. This further favors a uniform brightness distribution.

It is yet another embodiment that the front of the diffusion plate is a diffuser optically connected downstream. This further increased uniformity of the radiated light.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an embodiment, which will be described in more detail in conjunction with the drawings.

1 shows in plan view a lighting device;

2 shows the lighting device as a sectional view in side view; and

3 shows a more detailed excerpt from the 2 in the area of the first and second layer.

1 shows in plan view a lighting device 1 , The lighting device 1 has a circular disc-shaped, transparent diffusion plate 2 constant thickness of PLEXIGLAS Endlighten T on, on its circular edge 3 in the circumferential direction to a longitudinal axis L or symmetry axis a plurality of white light emitting light-emitting diodes 4 are arranged equally distributed. That of the light-emitting diodes 4 radiated white light gets through the edge 3 in the scattering plate 2 coupled ("edge lighting") and to a considerable extent on the front side shown 5 and the parallel back side 6 radiated (see 2 ). The light-emitting diodes 4 are arranged on a common flexible board, for. B. a light strip of the type Linear Light Flex from Osram. The scatter plate 2 and the light emitting diodes 4 are in a common housing 7 accommodated. The lighting device 1 may in particular be an LED module.

As in 2 and enlarged in 3 shown are at the back 6 multiple layers 8th . 9 arranged, namely four similar first layers 8th between the back 6 and the several first layers 8th a second layer 9 , The first layers 8th have color pigments of the color "absolutely white" (according to RAL), so they are from the scattering plate 2 through the back 6 Reflect light incident on them again in a color-neutral manner. The second layer 9 indicates in clearcoat 10 embedded as matrix material, cuboid glass particles 11 on. The glass particles 11 are transparent and have z. B. an edge length of about 0.25 mm × 0.1 mm to about 0.45 mm × 0.2 mm. The second layer 9 For example, it may have been made from a mixture of 95 milliliters of clearcoat and 5 grams of glass particles.

As in particular in 3 shown, the second layer over its thickness (or height), an uneven distribution of the glass particles 11 on, as these are at the back 6 the diffuser 2 focus. This is achieved by getting the glass particles 11 after applying the still liquid clearcoat 10 on the back 6 the scattering plate 2 settle or sediment and thus directly on the scattering plate 2 (without gap or gap) are arranged.

Distances over the front 5 the scattering plate 2 and this is optically downstream is a diffuser disc 12 for the diffusion of light passing through it.

During operation of the lighting device 1 becomes light of the LEDs 4 through the edge 3 in the scattering plate 2 coupled and from this through the front 5 and the back 6 radiated. Through the back 6 radiated light is first through the glass particles 11 distributed in the area and thus homogenized in terms of its brightness. Through the glass particles 11 scattered or reflected light is either back into the scatter plate 2 thrown back or meets after running through the clearcoat 10 on the first layer 8th , At the first layer, the light is reflected diffusely neutral in color and passes through the second layer after running 9 back into the scattering plate 2 one. On the front side 5 the scattering plate 2 radiated light passes through the diffuser disk 12 and can then be used as a useful light.

While the invention has been further illustrated and described in detail by the illustrated embodiment, the invention is not so limited and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

For example, you might like the diffuser disk 12 be waived.

Generally, "on", "an", etc. may be taken to mean a singular or a plurality, in particular in the sense of "at least one" or "one or more", etc., as long as this is not explicitly excluded, e.g. B. by the expression "exactly one", etc.

Also, a number may include exactly the specified number as well as a usual tolerance range, as long as this is not explicitly excluded.

LIST OF REFERENCE NUMBERS

1

lighting device

2

diffusion plate

3

edge side

4

led

5

Front of the diffusion plate

6

Rear side of the diffusion plate

7

casing

8th

first shift

9

second layer

10

clearcoat

11

glass particles

12

diffuser

L

longitudinal axis

Claims (13)

Lighting device ( 1 ), comprising - a light-transmitting diffusion plate ( 2 ) with a front side ( 5 ), a back side ( 6 ) and a side edge ( 3 ), - on which backside ( 6 ) at least one first reflective layer ( 8th ), which has diffusely reflecting color pigments, and furthermore comprising - at least one semiconductor light source ( 4 ), which optically with the edge side ( 3 ) of the scattering plate ( 2 ), wherein - between the back ( 6 ) of the scattering plate ( 2 ) and the first layer ( 8th ) a second layer ( 9 ), which particles ( 11 ) made of translucent material. Lighting device ( 1 ) according to claim 1, wherein the at least one first layer ( 8th ) has white color pigments. Lighting device ( 1 ) according to one of the preceding claims, wherein the at least one first layer ( 8th ) has multiple layers. Lighting device ( 1 ) according to any one of the preceding claims, wherein the second layer ( 9 ) Particles ( 11 ) made of transparent material. Lighting device ( 1 ) according to any one of the preceding claims, wherein the particles ( 11 ) Glass particles are. Lighting device ( 1 ) according to any one of the preceding claims, wherein the particles ( 11 ) have a maximum extension between 0.2 mm and 0.5 mm. Lighting device ( 1 ) according to any one of the preceding claims, wherein the particles ( 11 ) have a rectangular shape. Lighting device ( 1 ) according to any one of the preceding claims, wherein the particles ( 11 ) of the second layer ( 9 ) in a, in particular transparent, matrix material ( 10 ) are embedded. Lighting device ( 1 ) according to claim 8, wherein the particles ( 11 ) have a higher density than the matrix material ( 10 ). Lighting device ( 1 ) according to any one of the preceding claims, wherein the particles ( 11 ) of the second layer ( 9 ) with increased density at the back ( 6 ) of the scattering plate ( 2 ) are arranged. Lighting device ( 1 ) according to one of the preceding claims, wherein the at least one semiconductor light source ( 4 ) several around the edge ( 3 ) of the scattering plate ( 2 ), in particular evenly distributed, semiconductor light sources ( 4 ) having. Lighting device ( 1 ) according to one of the preceding claims, wherein the front side ( 5 ) of the scattering plate ( 2 ) a diffuser ( 12 ) is optically downstream. Method for producing a lighting device ( 1 ) according to claim 9, wherein the method comprises at least the following step: - applying the second layer ( 9 ) into the transparent matrix material ( 10 ) embedded particles ( 11 ) made of transparent material on the back ( 6 ) of the scattering plate ( 2 ) and - allowing the particles to settle ( 11 ) on the back ( 6 ) of the scattering plate ( 2 ).

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